By Mike Mawhinney in Syria

On the Popular Protection Units' (YPG) most forward position in their fight against Islamic State (IS), a Russian-made Mosin-Nagant bolt-action rifle from 1940 sits in the hands of an 18-year-old fighter.

It may lack the sophistication that is needed to fight IS in the Rojava, but he already handles it with experience.

The battered assortment of AK-47s slung on the shoulders of young men and women in the Kurdish militia group are also capable and effective.

Behind them, a 14.5mm KVPT heavy machine gun is mounted on the ubiquitous Toyota pick-up seen across the Middle East.

It spits heavy rounds in short bursts at a far-off IS position. Like all the weapons the Kurdish militia are wielding it is a crude and simple gun for waging war.

In front of them, IS are relying on snipers and 50mm mortars.

YPG's Forward Operating Base (FOB) is cold and dusty. The commander, Sozda Afrin, tells us that "the fighters only have just enough ammunition" and they often have to take weapons from IS fighters they kill to resupply.

US-led coalition jets circle high above. They bring the sophistication to the fight, striking numerous times on suspected IS positions about 2km from our position.

The airstrikes have driven IS back from their supply lines on the Turkish border, back to Raqqa and pushed them underground.

They have also empowered the Peshmerga in Iraq and the YPG to launch a number of successful offensives.

IS appears to be in a desperate state, sending in waves of inexperienced suicide bombers by foot or vehicle to penetrate Kurdish defences.

Most - if not all - are gunned down in no-man's land, caught in anti-vehicle-borne improvised explosive device (VBIED) trenches or exploding prematurely in the barren grassy plains.

They appear to no longer have the ability to outflank the YPG positions with experienced, hardened fighters capable of sizing objectives and repelling Kurdish counter attacks.

Airstrikes have reduced their effectiveness to conduct manoeuvrable warfare, reducing their numbers and pushing them into a subterranean world.

Air war alone is never really effective, as we have seen in recent conflicts from the Balkans to Africa to the Middle East.

The Kurds are in political speak the only "boots on the ground". The question is will it be enough to beat IS, or will the coalition need to provide more arms and training - and perhaps additional troops to get the job done.

(Sky News)